Milo- > I found sine waves will be terribly distorted when they are generated at > relatively high frequency(above 5khz) from signal source in GRC. I set the > sampl_rate of scope sink to 2Ghz(high enough, I think), and there are always > spikes on generated sine wave. This problem is especially distinct when > generated sine wave reaches 20Khz and the waveform displayed on scope sink > is almost "saw wave". There will be nothing to dispaly if I keep on > increasing frequency to 1Mhz. Is there anybody who met this problem before? > or it might only be the display problem in GRC? I guess it might be the > problem of scope sink which could not achieve that high sweep (sampling) > rate even I set it correctly. > > Attached are snapshot of generated sine waves at different frequencies:
Your plots are probably fine, depending on what is your sampling rate (Fs). Think of it this way: if you display a sine wave near Fs/2 then you only have 2 samples for each sine wave period (1 per peak) and connecting those dots with straight lines on a scope graph will look like "spikes", to use your terminology. In the case of your 20 kHz plot, it looks to me like you might have 3 or 4 or so samples per sine wave period, so my guess is your Fs is somewhere between 60 and 80 kHz. -Jeff _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
